ULTRASONICGENERATINGTOOTHBRUSH

Technical Field

[1] The present invention relates to an ultrasonic toothbrush, and more particularly, to an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, wherein an acoustic impedance transmission member for amplifying ultrasonic vibration is mounted between a toothbrush head and an ultrasonic vibrator so that the ultrasonic vibration can be effectively generated to minimize its power consumption, and multiple frequency outputs can be obtained to prevent stomatitis from recurring and to ef¬ fectively heal an oral inflammation. Background Art

[2] Generally, piezoelectric members have been widely used in ultrasonic elements, displacement generation elements, various kinds of sensors and the like in a variety of fields including electronics, communications and machines. Specifically, when an electric signal is applied to a piezoelectric member, the piezoelectric member may be contracted or expanded in accordance with the frequency of the applied electric signal. This feature allows the piezoelectric member to be utilized as an ultrasonic vibrator, sonar, a piezoelectric buzzer and speaker, an actuator, and the like. Meanwhile, with the use of electrical energy generated upon application of mechanical energy, a piezoelectric member can be utilized as a piezoelectric ignition element, various kinds of sensors, and the like. Further, a piezoelectric member may be used as a piezoelectric inverter that employs the two energy conversion effects.

[3] A phenomenon in which mechanical vibration is generated upon application of an electrical signal to a piezoelectric member is called an "inverse piezoelectric effect". Piezoelectric ceramic has been widely used for the generation of ultrasonic vibrator, because largest displacement occurs when a voltage with a frequency identical to a resonance frequency of the piezoelectric ceramic is applied thereto. The ultrasonic vibrator converts high frequency electric power into mechanical vibration which in turn is transmitted to a medium through a vibration member (conventionally, a horn made of metal) for transmitting and amplifying the mechanical vibration.

[4] Meanwhile, since a conventional electric toothbrush mechanically rotates bristles by using an electric motor, the surfaces of teeth can be cleaned but a fine interstice between the gum and the teeth cannot be cleaned. Further, it has been reported that strong brushing effects cause damage to weak gums. Thus, an injury that may be a cause of an inflammation may be generated in an oral cavity of an infant who is unfamiliar with the use of the toothbrush. Although a toothbrush in which the driving

frequency of an electromagnet is increased to an ultrasonic range, e.g. 300 times per second, has been commercialized, such a toothbrush has large amplitude and thus cannot solve disadvantages of an electric toothbrush. Further, since the vibration of 300 times per second is not expected to produce powerful cavitation effects, there is a problem in that it is difficult to expect sterilization and cleaning due to cavitation. [5] An ultrasonic toothbrush using a piezoelectric ultrasonic scheme for solving the problems has been accepted in medical circles due to its great usefulness and then commercialized. Since such an ultrasonic toothbrush using the piezoelectric ultrasonic scheme is constructed by attaching a piezoelectric member for generating ultrasonic vibration to a plastic portion to which bristles are mounted and it utilizes a thickness vibration mode of 1.6 MHz, ultrasonic waves generated from the piezoelectric member are attenuated by the plastic portion of the toothbrush. Thus, the ultrasonic toothbrush can hardly generate ultrasonic vibration and uses only effects resulting from ultrasonic acoustic transmission. Further, since products using the piezoelectric ultrasonic scheme employ a vibration motor scheme, they cannot produce effective ultrasonic vibration energy and cavitations effects using piezoelectric members. Therefore, there is a problem in that the aforementioned disadvantages of the vibration motor scheme have not yet been solved. Accordingly, there is a need for an effective ultrasonic toothbrush capable of simultaneously producing ultrasonic vibration and cavitation effects. Disclosure of Invention

Technical Problem

[6] The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, wherein ultrasonic vibration can be effectively transmitted to bristles of the toothbrush.

[7] Another object of the present invention is to provide an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, wherein a cavitation region is increased to improve cleaning and healing effects on the teeth and gum of a user.

[8] A further object of the present invention is to provide an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, wherein the intensity of the piezoelectric ultrasonic vibrator is increased to perform negative ionization of cleaning water contained in the oral cavity and to generate surfactant ions, thereby improving cleaning effects.

[9] A still further object of the present invention is to provide an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, wherein bristles can be easily mounted to minimize replacement costs of the bristles. Technical Solution

[10] According to an aspect of the present invention for achieving the objects, there is

provided an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, comprising a toothbrush body with a predetermined space formed therein, a toothbrush head including one side mounted to an end of the toothbrush body and the other side provided with bristles, a piezoelectric member mounted in the toothbrush body for generating ultrasonic vibration, an ultrasonic vibrator for amplifying the ultrasonic vibration received from the piezoelectric member and transmitting the amplified ultrasonic vibration to the toothbrush head, a power driving unit for supplying electric power to the ultrasonic vibrator, and an acoustic impedance transmission member provided between the toothbrush head and an end of the ultrasonic vibrator brought into contact with the toothbrush head to amplify the ultrasonic vibration.

[11] According to another aspect of the present invention, there is provided a n ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, comprising a toothbrush body with a predetermined space formed therein, a toothbrush head including one side mounted to an end of the toothbrush body and the other side provided with bristles, a piezoelectric member mounted in the toothbrush body for generating ultrasonic vibration, an ultrasonic vibrator for amplifying the ultrasonic vibration received from the piezoelectric member and transmitting the amplified ultrasonic vibration to the toothbrush head in accordance with a vibration mode expressed as nC / (4 xFr(λ/4)) = nλ/4, where λ is a wavelength, Fr(λ/4) is a resonant frequency, C is a sound speed in a metallic elastic member and n is an odd number, and a power driving unit for supplying electric power to the ultrasonic vibrator.

[12] According to a further aspect of the present invention, there is provided an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, comprising a toothbrush body with a predetermined space formed therein, a toothbrush head including one side mounted to an end of the toothbrush body and the other side provided with bristles, a piezoelectric member mounted in the toothbrush body for generating ultrasonic vibration, an ultrasonic vibrator for amplifying the ultrasonic vibration received from the piezoelectric member and transmitting the amplified ultrasonic vibration to the toothbrush head, and a power driving unit for supplying electric power to the ultrasonic vibrator, wherein a cross section of a leading end of the ultrasonic vibrator is formed to elongated in a direction and a cross section of a base end of the ultrasonic vibrator is formed to be elongated in a direction different from the elongation direction of the cross section of the leading end of the ultrasonic vibrator.

[13] According to a still further aspect of the present invention, there is provided an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator, comprising a toothbrush body with a predetermined space formed therein, a scaling device including one side mounted to an opened end of the toothbrush body and the other side connected to a water supply tube for supplying water thereto, an ultrasonic vibrator mounted in the

toothbrush body for generating ultrasonic vibration, amplifying the generated ultrasonic vibration and then transmitting the amplified ultrasonic vibration to the scaling device, and a power driving unit for supplying electric power to the ultrasonic vibrator.

Brief Description of the Drawings [14] Fig. 1 is a sectional view of an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator according to the present invention. [15] Fig. 2 is a perspective view showing the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [16] Fig. 3 is a view showing how to couple a toothbrush body and a toothbrush head in the ultrasonic toothbrush according to the present invention. [17] Fig. 4 is a diagram showing a vibration displacement occurring at a vibration mode of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [18] Figs. 5 and 6 show output current and voltage waveforms when the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush according to the present invention is operated, respectively. [19] Fig. 7 is a sectional view of another ultrasonic toothbrush using a piezoelectric ultrasonic vibrator according to the present invention. [20] Figs. 8 to 10 are a perspective view, a side view and a rear view of the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush according to the present invention, re¬ spectively. [21] Fig. 11 is a diagram showing a vibration displacement occurring at a vibration mode of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [22] Fig. 12 is a schematic view of a device for measuring the vibration displacement of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [23] Fig. 13 shows measurement results of the vibration displacement of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [24] Fig. 14 is a schematic view showing an underwater oscillation test for the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention. [25] Figs. 15 to 18 show results of the underwater oscillation test for the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention, re¬ spectively.

[26] Fig. 19 is a view showing a current waveform analyzer for analyzing a current waveform according to a tilt angle of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention.

[27] Figs. 20 and 21 are views showing current waveforms and FFT analysis results when a load is not applied and is applied to an end of the piezoelectric ultrasonic vibrator, respectively, in a case where the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention has a tilt angle of 45 degrees.

[28] Figs. 22 and 23 are views showing current waveforms and FFT analysis results when a load is not applied and is applied to an end of the piezoelectric ultrasonic vibrator, respectively, in a case where the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention has a tilt angle of 0 degree.

[29] Fig. 24 is a view showing resonance frequency analysis results for the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention, using HP4194A.

[30] Figs. 25 to 27 are views showing FEM analysis results for a vibration mode of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention.

[31] Fig. 28 is a view showing another embodiment in which a scaling device is mounted to the ultrasonic toothbrush according to the present invention. Best Mode for Carrying Out the Invention

[32] Hereinafter, preferred embodiments of an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator according to the present invention will be described in detail with reference to the accompanying drawings.

[33] Fig. 1 is a sectional view of an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator according to the present invention, and Fig. 2 is a perspective view showing the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush.

[34] As shown in Figs. 1 and 2, the ultrasonic toothbrush using the piezoelectric ultrasonic vibrator according to the present invention comprises a toothbrush body 500 with a predetermined space formed therein, and a toothbrush head 600 of which one side is mounted to an end of the toothbrush body 500 and the other side is provided with bristles 610. In this case, a piezoelectric member 200 for generating ultrasonic vib ration, an ultrasonic vibrator 100 for amplifying the ultrasonic vibration received from the piezoelectric member 200 and transmitting the amplified ultrasonic vibration to the toothbrush head 600, a power driving unit 300 for supplying electric power to the ultrasonic vibrator 100, and an acoustic impedance transmission member 400 provided between the toothbrush head 600 and an end of the ultrasonic vibrator 100, which is brought into contact with the toothbrush head 600, to amplify the ultrasonic vibration

are installed within the predetermined space of the toothbrush body 500.

[35] Specifically, the power driving unit 300 is installed at a side of the interior of the toothbrush body 500 and comprises a rechargeable battery pack 310 for supplying electric power and a driving circuit 320 electrically connected to the rechargeable battery pack 310 to generate ultrasonic vibration, which are installed within the toothbrush body 500 with a partition 510 disposed therebetween. In this case, the driving circuit 320 is electrically connected through two electric wires 330 to ring-type metal electrodes 110 that are positioned close to the piezoelectric member 200.

[36] Further, a rear metallic elastic member 120 is installed within the toothbrush body

500 to be adjacent to the power driving unit 300 with an isolation plate 520 positioned therebetween. The rear metallic elastic member 120 is supported by a silicone elastic rubber 530 and is connected to the ultrasonic vibrator 100 through a coupling member 170. The ultrasonic vibrator 100 will be described in detail later.

[37] The coupling member 170 is positioned between the rear metallic elastic member

120 and the ultrasonic vibrator 100 to connect the rear metallic elastic member 120 to the ultrasonic vibrator 100. In this embodiment, a bolt of which both ends are screwed into the rear metallic elastic member 120 and the ultrasonic vibrator 100 is used as the coupling member 170. Further, two ring-type piezoelectric members 200 and two ring- type metal electrodes 110 electrically connected to the driving circuit 320 are arranged in parallel around the coupling member 170. An insulation member 180, e.g. a polymer insulation tube, is inserted around the coupling member 170 to prevent the ring-type metal electrodes 110 and the piezoelectric members 200 from coming into electrical contact with each other.

[38] Further, the toothbrush body 500 is provided with a silicone rubber packing 540 for firmly fixing the ultrasonic vibrator 100 to fix an outer peripheral surface of a base of the ultrasonic vibrator 100, and is coupled with the toothbrush head 600 such that the other end of the fixed ultrasonic vibrator 100 is brought into contact with an inner surface of the toothbrush head 600. In this case, the acoustic impedance transmission member 400 is mounted on the other end of the ultrasonic vibrator 100 so that it can be controlled to transmit optimal ultrasonic vibration.

[39] The acoustic impedance transmission member 400 is mounted at an angle of 0 to

45 degrees and is preferably made of a material with an acoustic impedance similar to that of the ultrasonic vibrator 100. The acoustic impedance of the acoustic impedance transmission member 400 is determined by multiplying the density of material thereof by a sound speed therein, and it is preferred that the acoustic impedance transmission member 400 be made of a selected material, which has a density and a sound speed similar to those of the ultrasonic vibrator and has excellent wear resistance since the ultrasonic vibrator 100 vibrates at an ultrasonic speed. For example, the acoustic

impedance transmission member 400 may be made of Econol, carbon fiber-reinforced plastic, bakelite, polyamide, glass embedded Teflon (GET), and the like. Alternatively, a carbon film similar to diamond, a titanium nitride coating or a titanium- aluminum nitride coating may be formed on the end of the ultrasonic vibrator 100 and the acoustic impedance transmission member 400. As described above, the acoustic impedance transmission member 400 is formed as an acoustic impedance matching layer that can transmit the ultrasonic vibration of the ultrasonic vibrator without loss and simultaneously has wear resistance, thereby improving vibration characteristics of the ultrasonic toothbrush. Further, since the tilt angle of the acoustic impedance transmission member can be controlled, it is possible to variously control the amplitude and direction of the vibration of the bristles 610.

[40] Fig. 3 is a view showing how to couple the toothbrush body and the toothbrush head in the ultrasonic toothbrush using the piezoelectric ultrasonic vibrator according to the present invention.

[41] As shown in Fig. 3, a locking groove 550 provided with a leaf spring 570 for maintaining a certain coupling force is formed along an outer periphery of an end of the toothbrush body 500 where the toothbrush body 500 is coupled with the toothbrush head 600. A locking ridge 560, which will be fitted into the locking groove 550, is formed at an end of the toothbrush body 600 coupled to the end of the toothbrush body 500.

[42] Meanwhile, it is preferred that the coupled potions of the ultrasonic vibrator 100 and the toothbrush head 600 be made of a synthetic resin containing minerals such as amethyst or tourmaline capable of emitting negative ions under external pressure and the ultrasonic vibrator 100 be made of stainless steel, aluminum, titanium alloy, duralumin, metallic elastic, or the like. When the vibration of the ultrasonic vibrator 100 is transmitted to the toothbrush head 600, pressure is applied to the minerals in the synthetic resin to thereby increase the generation of negative ions.

[43] Next, the ultrasonic vibrator used in the present invention will be described in detail.

[44] The ultrasonic vibrator 100 comprises a vibratory diaphragm 130 provided at the base thereof, a vibration coupling bar 140 extending from the vibratory diaphragm 130, and abraded surfaces 160 formed by removing some portions at both sides of a leading end of the vibration coupling bar 140. In this case, it is preferred that the ultrasonic vibrator 100 be anodized, chrome-plated or titanium-coated to eliminate an oxidation phenomenon due to an alkaline solution when it is manufactured using an aluminum based metal.

[45] Fig. 4 is a diagram showing a vibration displacement occurring at a certain vibration mode of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush

according to the present invention, and Figs. 5 and 6 show output current and voltage waveforms when the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush according to the present invention is operated, respectively.

[46] As shown in Figs. 4 to 6, the vibration amplitude can be controlled according to the length of the vibration coupling bar 140. Here, the vibration displacement of the ultrasonic vibrator 100 corresponds to 'a' in Fig. 4 and is in λ/4 mode. When the ultrasonic vibrator 100 is actually operated at a frequency of 45 kHz, the length of the ultrasonic vibrator 100 can be calculated using the following equation:

[47] C / (4 xFr(λ/4)) = λ/4, (1)

[48] where λ is a wavelength, Fr(λ/4) is a resonant frequency in λ/4 mode, and C is a sound speed in a metallic elastic member. In this equation, if Fr(λ/4) is 45 kHz and C is substituted with 5130 m/s in case of 60 series duralumin, λ/4 becomes of 28.5 mm. At this time, the frequency range of 45 kHz selected in the embodiment of the present invention is determined based on a clinical report that pain delivered through surfaces of the teeth can be minimized at a frequency equal to or greater than 40 kHz, and is also a value set to allow the toothbrush to be used for both brushing and scaling functions through the replacement of the bristles 610 with a scaling device 700 to be described later.

[49] As such, considering a horn shape parameter of the ultrasonic vibrator 100, the length of the ultrasonic vibrator 100 is measured to be 28.5 mm to 35 mm, and the length thereof where maximum displacement occurs is experimentally determined.

[50] Meanwhile, referring again to Fig. 4, if the length of the rear metallic elastic member 120 is equal to that of the ultrasonic vibrator 100 with respect to a node 'b' of the piezoelectric member 200, the vibration displacement has the vibration amplitude such as 'c' in Fig. 4. However, this embodiment is constructed such that the length of the rear metallic elastic member 120 is shorter than that of the ultrasonic vibrator 100, thereby further increasing the generation of ultrasonic vibration in a front direction of the toothbrush. At this time, an actual vibration displacement generated in the rear metallic elastic member 120 decreases as indicated in 'd' of Fig. 4.

[51] When the ultrasonic vibrator 100 thus designed is driven using the driving circuit

320 connected to a 6V battery, the output current and voltage waveforms of the ultrasonic vibrator 100 are represented as shown in Figs. 5 and 6, respectively.

[52] Since the current was adjusted to the scale of 2 mA/mV using Tektronix P6021 AC

Probe, the output current is about 0.07 Arms and the output voltage is 150 Vrms, by which a power of 10.5 W is in turn obtained.

[53] Fig. 7 is a sectional view of an ultrasonic toothbrush using a piezoelectric ultrasonic vibrator according to a modified embodiment of the present invention, and Figs. 8 to 10 are a perspective view, a side view and a rear view of the piezoelectric ultrasonic

vibrator of Fig. 7, respectively.

[54] As shown in Figs 7 to 10, the vibration coupling bar 140 of the ultrasonic vibrator

100 may comprise a first vibration coupling bar 140a extending from the vibratory diaphragm 130, a second vibration coupling bar 140b extending from a leading end of the first vibration coupling bar 140a and having a diameter smaller than that of the first vibration coupling bar 140a, and a third vibration coupling bar 140c extending from a leading end of the second vibration coupling bar 140b and having a diameter smaller than that of the second vibration coupling bar 140b.

[55] For example, the first vibration coupling bar 140a has a diameter of 7 mm, the second vibration coupling bar 140b has a diameter of 5 mm, and the third vibration coupling bar 140c has a diameter of 3 mm such that the diameters of the three vibration coupling bars are sequentially reduced by 2 mm. Further, the lengths of the first, second and third vibration coupling bars 140a, 140b and 140c may be set to 27 mm, 33 mm and 31 mm, respectively, and abraded surfaces 160 may be formed such that an end of the third vibration coupling bar 140c has a thickness of 2 mm to change vibration intensity at the vibration mode.

[56] Fig. 11 is a diagram showing a vibration displacement occurring at a certain vibration mode of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush according to the present invention.

[57] In such a configuration, when the ultrasonic vibrator 100 is operated at a certain driving frequency in 3λ/4 mode, the length of the vibration coupling bar 140 can be determined according to the following equation. When the ultrasonic vibrator 100 is operated at a frequency of 45 kHz in 3 /4 mode, the equation used to calculate the length of the ultrasonic vibrator 100 is expressed as follows:

[58] 3C / (4 xFr(λ/4)) = 3λ/4 (2)

[59] As for the length of the ultrasonic vibrator 100 according to the equation, 3λ/4 becomes 28.5 3 = 85.5 mm when the ultrasonic vibrator 100 is operated at a frequency of at 45 kHz. Considering the shape effects of the ultrasonic vibrator, the maximum displacement is experimentally determined for the horn with a length of 85.5 mm to 98 mm. At this time, the vibration displacement of a front horn with respect to node 'b' becomes as indicated on 'a' of Fig. 11.

[60] As described above, an equation for calculating the length of the ultrasonic vibrator

100 is expressed, as follows:

[61] nC / (4 xFr(λ/4)) = nλ/4, (3)

[62] where λ is a wavelength, Fr(λ/4) is a resonant frequency in λ/4 mode, C is a sound speed in a metallic elastic member, and n is an odd number, i.e. 1, 3, 5

[63] Meanwhile, referring again to Figs. 8 to 10, the cross section of a leading end of the ultrasonic vibrator 100 is formed to be elongated in a direction, and the cross section of

a base end of the ultrasonic vibrator 100 is formed to be elongated in a direction different from the elongation direction of the cross section of the leading end of the ultrasonic vibrator 100, so that the ultrasonic vibration caused by the piezoelectric member 200 may result in multiple frequency vibration due to simultaneous occurrence of longitudinal, bending and torsional vibrations.

[64] For example, in this embodiment, the vibratory diaphragm 130 in the form of a rectangle with rounded corners is formed at the base end of the ultrasonic vibrator 100, and the vibration coupling bar 140 with a shape corresponding to smaller than the rectangular shape of the vibratory diaphragm 130 is formed at the leading end of the ultrasonic vibrator 100. Since the cross section of the vibration coupling bar 140 is formed to be angularly offset by 40 to 60 degrees with respect to the cross section of the vibratory diaphragm 130, the longitudinal, bending and torsional vibrations can be simultaneously generated in the ultrasonic vibration.

[65] For example, a linear portion 151 of an interface corresponding to the cross section of the vibratory diaphragm 130, which will be described later, and the abraded surfaces 160 corresponding to the cross section of the vibration coupling bar 140 may be designed such that an angle θ' defined between the linear portion and the abraded surfaces is 45 degrees. At this time, the interface 150 is an outer peripheral surface of the vibratory diaphragm 130 of the ultrasonic vibrator 100 and comprises the upper and lower linear potions 151 and curved portions 152 for curvilinearly connecting the linear portions 151.

[66] Fig. 12 is a schematic view of a device for measuring the vibration displacement of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush capable of providing the multiple frequency output according to the present invention, and Fig. 13 shows measurement results of the vibration displacement of the piezoelectric ultrasonic vibrator of the ultrasonic toothbrush capable of providing the multiple frequency output according to the present invention.

[67] As shown in Fig. 12, the measuring device for measuring the vibration dis¬ placement of the ultrasonic vibrator is set up in such a manner that the ultrasonic vibrator 100 stands upright on a bottom surface 53 of a hydraulic cylinder 52 and a hollow rectangular jig 54 is installed between a leading end of the ultrasonic vibrator 100 and a fixed top portion 56 of a hydraulic press 55. After a load of 10 kgf is applied to the ultrasonic vibrator 100, vertical and horizontal vibration displacements are measured using two vibration displacement sensors 57 and 58 for detecting vertical and horizontal vibration displacements, respectively. The measurement results are shown in Fig. 13.

[68] As shown in Fig. 13, if the tilt angle θ' of the abraded surfaces 160 is 0 degree, a vertical vibration displacement 61 is produced while a horizontal vibration dis-

placement 62 is not almost produced. However, if the tilt angle θ' of the abraded surfaces 160 is 40 to 50 degrees, it is understood that the vertical and horizontal vibration displacements 61 and 62 are maximally produced at the same time.

[69] In order to verify that the vertical and horizontal vibration displacements 61 and 62 are maximally produced at the same time in a case where the tilt angle θ' of the abraded surfaces 160 is 40 to 50 degrees, an underwater oscillation test was performed using an aluminum foil.

[70] Fig. 14 is a schematic view showing the underwater oscillation test for the ultrasonic vibrator in the ultrasonic toothbrush capable of providing multiple frequency outputs according to the present invention, and Figs. 15 to 18 show measurement results of the underwater oscillation test for the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush capable of providing the multiple frequency outputs according to the present invention, respectively.

[71] As shown in Fig. 14, the measurement results in which the ultrasonic vibrator 100 has been oscillated for 30 minutes when the side of the ultrasonic vibrator, i.e., the abraded surface 160 is positioned in parallel with an aluminum foil 73 and the end of the abraded surface 160 is also positioned perpendicular to an aluminum foil 74 in a state where water 72 is poured into a water tank 71 are as follows.

[72] First, in a case where the abraded surface 160 is positioned in parallel with the aluminum foil 73, i.e. the tilt angle θ' of the abraded surfaces 160 is 0 degree, it is observed that no hole 82 is generated in aluminum foil 73 by means of the cavitation as shown in Fig. 15. However, in a case where the tilt angle θ' of the abraded surfaces 160 is 45 degrees, it is observed that holes 82 are generated in the aluminum foil 73 by means of the cavitation as shown in Fig. 16.

[73] Further, in a case where the abraded surface 160 is positioned perpendicular to the aluminum foil 74, holes 82 are generated by means of the cavitation regardless of the tilt angle. That is, in a case where the tilt angle θ' of the abraded surfaces 160 is 0 degree, it is observed that holes 82 are generated in a surface perpendicular to the end of the abraded surfaces 160 by means of the cavitation as shown in Fig. 17. Furthermore, in a case where the tilt angle θ' of the abraded surfaces 160 is 45 degrees, it is observed that holes 82 are generated over a wide range by the cavitation on the end of the horn, as shown in Fig. 18.

[74] As described above, if the tilt angle θ' of the abraded surfaces 160 is 45 degrees, it can be observed that the longitudinal, torsional and bending vibrations are simul¬ taneously generated and thus the holes 82 are generated in the surfaces parallel with or perpendicular to the abraded surfaces 160 by means of the cavitation.

[75] Fig. 19 is a view showing a current waveform analyzer for analyzing a current waveform according to the tilt angle of the piezoelectric ultrasonic vibrator of the

ultrasonic toothbrush capable of providing the multiple frequency outputs according to the present invention.

[76] In order to illustrate such a phenomenon, as shown in Fig. 19, a driving circuit 92 is connected to a power supply 91 and a non-contact Tektronix P6021 AC Probe 95 is installed on a power input wire 94 for connecting the ultrasonic vibrator 100 and an output end of the driving circuit 92 to adjust the current to the scale of 2 mA/mV. Figs 20, 21, 22 and 23 show the current waveforms and FFT analysis results analyzed by using a Tektronix TDS3034 Oscilloscope 96 after the ultrasonic vibrator 100 has been operated.

[77] Figs. 20 and 21 are graphs illustrating the current waveforms and FFT analysis results in a case where the tilt angle of the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush capable of providing the multiple frequency outputs according to the present invention is 45 degrees. Figs. 20 and 21 show the results obtained when no load and a load of 10 kgf are applied to the end of the ultrasonic vibrator, respectively, in a case where the tilt angle of the ultrasonic vibrator is 45 degrees. In these figures, the numbers shown in the lower graph are frequency analysis results.

[78] For example, when no load is applied to the ultrasonic vibrator 100, frequency components corresponding to an integral multiple of 22 kHz, e.g., 22 kHz (® in Fig. 20), 44 kHz ( © in Fig. 20), 66 kHz (® in Fig. 20), 88 kHz (®in Fig. 20), 110 kHz (©in Fig. 20), 132 kHz (©in Fig. 20), etc. are occur from the left to the right as shown in Fig. 20. On the other hand, when a certain applied to the ultrasonic vibrator 100, the current value is increased from 60.2 mA to 62.2 mA and the frequency components corresponding to an integral multiple of 44 kHz, e.g. 44 kHz (© in Fig. 21), 88 kHz (® in Fig. 21), 132 kHz (© in Fig. 21), etc. are increased, so that the peaks corresponding to an integral multiple of 22 kHz can be clearly observed.

[79] Figs. 22 and 23 are graphs illustrating the current waveforms and FFT analysis results in a case where the tilt angle of the abraded surface of the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush capable of providing the multiple frequency outputs according to the present invention is 0 degree. Figs. 22 and 23 show the results obtained when no load and a load of 10 kgf are applied to the end of the horn, respectively, in a case where the tilt angle θ' of the abraded surface 160 is 0 degree.

[80] As shown in Figs. 22 and 23, it is observed that the current value is slightly increased when a load of 10 kgf is applied to the end of the horn but the frequency components corresponding to an integral multiple of 44 kHz, e.g. frequency components represented as ©, ®, and © in Fig. 21, do not occur. Accordingly, it is understood that the vibration mode is further increased when the tilt angle θ' of the abraded surfaces 160 is 45 degrees as compared with when the tilt angle θ' of the

abraded surfaces 160 is 0 degree.

[81] Fig. 24 is a graph showing resonance frequency analysis results for the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush capable of providing the multiple frequency outputs according to the present invention, using HP4194A.

[82] Fig. 24 shows the resonance frequency analysis results for the horn of the ultrasonic vibrator 100 configured as shown in Fig. 2, by using HP4194A. As shown in Fig. 24, low impedance regions are observed at a frequency near 22 kHz (® in Fig. 24), 44 kHz (© in Fig. 24), 66 kHz (® in Fig. 24), 88 kHz (® in Fig. 24), 110 kHz (© in Fig. 24), 132 kHz (© in Fig. 24), etc. regardless of the tilt angle. From the foregoing, it is understood that only the frequency components corresponding to an integral multiple of 22 kHz among a variety of high frequency components are filtered to drive the horn.

[83] Figs. 25 to 27 are views showing FEM analysis results for the vibration mode of the piezoelectric ultrasonic vibrator in the ultrasonic toothbrush capable of providing multiple frequency outputs according to the present invention.

[84] The vibration mode of the ultrasonic vibrator configured as shown in Fig. 7 is represented as simultaneously including the longitudinal vibration shown in Fig. 25, the torsional vibration shown in Fig. 26 and the bending vibration shown in Fig. 27. Such vibrations can be lowered or increased depending on the tilt angle θ' of the abraded surfaces 160. In particular, in a case where a certain load is applied to the end of the ultrasonic vibrator 100, it is understood that the vibration is lowered when the tilt angle θ' defined between the abraded surfaces 160 and the interface 150 is 0 degree, whereas the vibration is not restrained when the tilt angle θ' defined between the abraded surfaces 160 and the interface 150 is 45 degrees. Such a phenomenon results from the fact that the resultant vibration magnitude occurring at a region where the vibration of the linear portion 151 of the interface 150 and the vibration of the curved portion 152 thereof are superimposed.

[85] Accordingly, in a case where the bristles 610 are mounted to the end of the ultrasonic vibrator 100 with a predetermined load, the ultrasonic vibration can be ef¬ fectively transmitted to the bristles 610 by configuring the ultrasonic toothbrush such that the tilt angle θ' defined between the abraded surfaces 160 and the interface 150 is about 45 degrees.

[86] Fig. 28 is a sectional view showing another embodiment in which a scaling device is mounted to the ultrasonic toothbrush according to the present invention.

[87] As shown in Fig. 28, a scaling device 700 with the acoustic impedance transmission member 400 formed at a side thereof can be mounted to the toothbrush body 500. That is, a water supply tube 710 for supplying water is provided at a side of the scaling device 700 such that water can be ultrasonically vibrated due to the ultrasonic wave applied thereto by the ultrasonic vibrator 100 to thereby remove plaque on the teeth

through the cavitation occurring in the water. Furthermore, although no water is supplied, it is possible to remove visible plaque by means of the ultrasonic vibration of the scaling device 700.

[88] In addition, the principle of cleaning the teeth using the ultrasonic wave will be explained. When the ultrasonic vibrator 100 is operated, positive hydrogen ions and hydroxyl ions (OH ^" ) are generated due to an additional electrolysis. In such a case, electrons are provided to the positive hydrogen ions to generate hydrogen, while the hydroxyl ions (OH ) react with water (H O) to generate surface active agents, "H O ." Therefore, the cleaning efficiency of the ultrasonic toothbrush can be improved.

[89] In other words, when the ultrasonic toothbrush of the present invention is operated, the cavitation occurs in a solution in which the toothpaste, water and oral liquid in the oral cavity are mixed with one another. Due to the cavitation, a high temperature and pressure state of about 3300K and a pressure of 313 atm is maintained, and thus, water molecules and volatile are thermally decomposed. At this time, there are hydroxyl ions (OH ) of about 4 mM in the solution near the cavitation region such that the hydroxyl ions in an interface of the cavitation region can react with water molecules to generate surface active agents, "H O ." Therefore, the cleaning efficiency can be improved and the water is alkalescent.

[90] According to the present invention, since the cavitation region generated by the ultrasonic wave is increased due to the vertical/horizontal and rotational motions of the ultrasonic vibrator 100, an amount of hydroxyl ions generated can be maximized. Further, since the ultrasonic wave is transferred to the solution through the bristles 610, strong cavitation occurs at the gum and teeth and is then transferred throughout the gum and teeth. Therefore, there is an advantage in that soft plagues, bacteria and the like can be sterilized and removed.

[91] Hereinafter, the operation of the present invention configured as described above will be described.

[92] First, when electric power is supplied from the rechargeable battery pack 310 of the power driving unit 300 provided in the toothbrush body 500 to drive the driving circuit 320 capable of generating multiple frequency outputs, a voltage is applied to the ring- type metal electrodes 110 from the driving circuit 320 through the electric wires 330 to vibrate the piezoelectric member 200. At this time, as the piezoelectric member 200 is operated, the longitudinal, bending and torsional vibrations are simultaneously produced in the ultrasonic vibrator 100 to thereby generate the multiple frequency vibrations.

[93] That is, when the vibrations of the piezoelectric member 200 are transmitted to the ultrasonic vibrator 100, the acoustic impedance transmission member 400 provided at the end of the ultrasonic vibrator 100 is also operated to vibrate the bristles 610

provided near the toothbrush head 600 such that the teeth can be washed and cleaned.

[94] At this time, the abraded surfaces 160 formed by removing some portions at both sides of the leading end of the ultrasonic vibrator 100 are angularly offset by a pre¬ determined angle with respect to the interface 150 formed at the base end of the ultrasonic vibrator 100. Thus, the longitudinal, bending and torsional vibrations are si¬ multaneously generated such that the multiple frequency vibrations can be generated. Accordingly, the powerful washing and cleaning of the teeth can be performed.

[95] According to the present invention as described above, since a predetermined angle is provided between the abraded surfaces 160 and the interface 150, the longitudinal, bending and torsional vibrations of the ultrasonic vibrator 100 can be simultaneously generated to thereby increase the cavitation region generated by the ultrasonic wave.

[96] Further, since the harmonics of multiple frequency components generated from the rectangular wave of an oscillating frequency are combined with the filtering effect due to the resonance phenomenon of the piezoelectric ceramic, the bristles 610 can be operated with the multiple frequency components. Therefore, a variety of cavities with a size or intensity of 400 D to several D can be generated. As a result, the sterilization and cleaning effects can be obtained due to the maximum cavitation, regardless of the shape and position of the object to be cleaned.

[97] Furthermore, since the bristles 610 can be finely vibrated at a frequency of 22 kHz,

44 kHz and 66 kHz in accordance with the longitudinal, bending and torsional vibration mode, the mechanical brushing effect with minimized impulse applied to the gum can be obtained.

[98] According to the ultrasonic toothbrush using the piezoelectric ultrasonic vibrator of the present invention, the bristles can be replaced more easily and the ultrasonic waves generated from the ultrasonic vibrator can also be transmitted through the bristles to the oral cavity. Further, the bristles can be easily replaced with the scaling device, and the cavitation region can also be increased. Therefore, there is an advantage in that the cleaning and treating effects for the teeth and gum can be enhanced.

[99] Further, as the intensity of the ultrasonic vibrator is increased, the cleaning water contained in the oral cavity can be ionized and the surfactant ions can be generated. Therefore, there is another advantage in that the cleaning effect can be further enhanced.

[100] Although the present invention has been described and illustrated in connection with the specific embodiments, it will be apparent to those skilled in the art that various modifications and changes can be made thereto within the spirit and scope of the present invention. Therefore, it is obvious that the true scope of the present invention should be defined by the appended claims.